<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
			//js定义变量var
			var x =10;
			var y =20;
			
		console.log(x+y);
			var a= 10 ,b=20;
			console.log(x);//10
			console.log(a*b);
			var x=100;
			
			
			console.log(x);//100 js语言非常灵活，再次声明可覆盖前面的值
		console.log(typeof(x));
		var x ="acv";
		console.log(typeof(x));
		
		</script>
	</head>
	<body>
	</body>
</html>
